Backflow preventers are used to prevent contamination of a building and/or public water distribution system by reducing or eliminating backflow of a contaminated hazardous fluid into the respective system(s). Conventional backflow preventers are mechanically sophisticated devices, that are threaded for pipes, unthreaded for tubing, or flanged at each end so they can be installed, i.e., spliced into the piping system. Conventional backflow preventers require periodic inspection, testing, maintenance and repair. Therefore, they must be visible and accessible. As such they are not tamper resistant or tamperproof. A conventional backflow preventer is usually, but not always, installed in a pipeline between a main municipal water supply line and a service line that feeds an installation, e.g., hospital, industrial building, commercial establishments, multiple or single family residences. A conventional backflow prevention valve is an assembly that typically includes two check valves that are configured to permit fluid flow in one direction, such as from a main municipal water supply distribution pipe system to a particular building's service (pipe) line. They are generally costly to purchase and, always labor intensive to install. Conventional backflow preventers are commonly used in buildings equipped with chemical processing equipment, sprinkler systems, etc. Backflow preventers are required by applicable plumbing codes to protect a building's potable water supply from accidental contamination, a condition that would occur from a cross connection and flow reversal in a branch or pipe riser, due to a process or system malfunction. Left unchecked, hydraulic reversal can compromise the quality and safety of a building's potable water supply system and, potentially, the municipal water supply distribution system as well. Nonetheless, current plumbing design and operating codes are essentially silent regarding protective measures against the willful intent of an individual (such as, for example, a terrorist, criminal, etc.) to inject a toxic contaminant into a building's potable water supply plumbing system and possibly the municipal water supply system, including fire hydrants, as well.
Historically, a typical backflow preventer consisted of a mechanical single spring-loaded check valve in a water supply line, generally placed between a pair of gate-type shutoff valves. Current building codes, however, now require backflow preventers to include a pair of independently spring-loaded positive check valves. The motivation behind such a rule is that should one of the check valves fail, the second valve can serve as a backup. Because of their mechanical complexity, current plumbing codes typically require that the check valve(s) be replaceable and repairable while on-line, that is, without shutting down the system. In contrast, current plumbing codes for commercial, industrial, multi-story residential buildings and single homes do not require the installation of backflow preventers. This leaves such buildings' internal potable drinking water supply vulnerable to compromise via injection of a toxic chemical or biological contaminant into the building's water supply system, with the added possibility of contaminating the municipal water supply distribution system in the process. The latter could compromise the water quality of an entire regional water distribution grid. In light of the health and safety concerns previously described, it is imperative that appropriate measures be immediately initiated to address and bridge this critical gap in security as it relates to existing and future potable drinking water systems.
While municipal codes generally require the replacement of single check valves with a double check valve backflow preventer, simply requiring building owners to undertake major re-plumbing to install these backflow preventers between the municipal water service distribution lines located in the street and downstream of the building's water meter would not address the vulnerability to intentional internal contamination within a given building. Retrofitting a conventional backflow preventer to protect a building's internal potable water distribution system from possible intentional contamination at every point-of-use water supply terminus, such as, for example, via shutoff valves for kitchen and bathroom fixtures, drinking water fountains, etc., could be very expensive. Each existing supply line would have to be re-plumbed to provide space to accommodate a single conventional check valve assembly. Moreover, access for repair and replacement must be provided for each such back flow preventer to provide for proper maintenance, since these devices are generally internally mechanically complex. Even in new construction, installation of conventional back flow preventers for each point-of-use fixture would be costly.
As noted in a Jun. 18, 2004 article entitled “Cross Connection Control Programs And Backflow Preventers Are Essential Components of Safe Drinking Water Systems,” published on Backflow Prevention TechZone (a trade web site at URL http://www.backflowpreventiontechzone followed by .com), plumbing system cross connections between potable and non-potable water supplies, water using equipment, and drainage systems, continue to be a serious potential public health hazard worldwide. Anywhere people congregate and utilize communal water supplies, water using equipment, and drainage systems, the danger of un-protected cross connections continue to threaten public health. Thus, there is a widening recognition that properly installed, maintained, and tested backflow prevention devices are critical elements of safe drinking water systems in our communities and workplaces. The report further noted that backflow preventer device development, beyond simple check valves, began to accelerate and diversify in the mid-20th century, but potable (“city”) water piping systems and water using equipment, especially inside industrial and medical buildings, have grown exponentially in complexity and are also continuously altered. Surveys over the decades have shown that water using devices and equipment which can contaminate a drinking water system continue to be connected to potable waterlines without properly selected, permitted, installed, maintained, and if appropriate for the device, tested and certified, backflow preventer valves. Thus, “despite decades of new public health and occupational safety laws, as well as updated and revised plumbing codes, along with new improved backflow preventer devices, the cross connection problem continues to be an ongoing dynamic one.”
The most universal backflow hazards are constantly re-created, such as in cross-connections within residential and public washrooms, and ordinary, unprotected from backflow, hose connections. The bathroom continues to be a repository of one of the subtle yet potentially dramatic backflow hazards found recurrently in homes and public places. Many local health departments have “blue water” flowing from the kitchen sink reports in their archives, which may well be only the tip of the iceberg of un-documented incidents of actual backflow from an unapproved or improperly installed toilet fill-valve assembly.
As further noted in the report cited above, recent cross connection inspection surveys (USC/FCCCHR) continue to reveal that the most prevalent and potentially hazardous potable water plumbing cross connection is the common hose connection (or hose bib) (UF/IFAS, 3/95) found in virtually every home and building. The predominant cause for the cross connection, known as backsiphonage, is the sudden and significant loss of hydraulic pressure in the water main. Excessive drops in water pressure, have historically, been attributed to a broken water main, a fire nearby where the Fire Department is using large quantities of water, or by a water company official opening a fire hydrant to test it. Buildings near a municipal water main break or a fire hydrant being opened will experience a lowering of the water pressure and possibly backsiphonage.
Conventionally, potable water backflow protection has been addressed by various valve types, having unique design configurations. Such designs include, for example, Air Gap, Atmospheric Vacuum Breaker, Pressure Vacuum Breaker, Double Check Valve, and Pressure Reducer. Such devices are external in their intended application, limited to a specific installation orientation, e.g., vertical or horizontal, visible, must be easily accessible and are thus vulnerable to tampering, are mechanically complex to the extent that periodic inspections and maintenance are required and without proper servicing are unreliable in the long term, and are operationally affected by gravity in whole or part.
For example, the air gap backflow preventer, considered by some to be the “ultimate” backflow preventer, is totally reliant on gravity to operate properly, and must be installed in an external manner. In addition, all conventional backflow preventers, because of their inherent design, are prone to clogging and fouling. Four of the five aforementioned must utilize a plurality of individual valve means and springs to prevent backflow. Such mechanical complexity actually fosters corrosion, clogging and/or fouling, and thus are unsuitable to resolve in a cost-effective manner the aforementioned public drinking water supply safety concerns. Additionally, conventional backflow valves require a great deal of effort in both labor and material to be installed, and as a result of their design must always be readily accessible, i.e., exposed, to provide for required periodic maintenance. Such valves thus offer a perfect access point for a terrorist.
A recent GAO-04-29 report to the United States Senate Committee on Environment specifically referenced fire hydrants as a top vulnerability. Moreover, as recently reported by the American Water Works Association on May 2, 2007, terror training manuals found in Afghanistan showed plans to contaminate America's water supply.
Thus, there is a compelling need for a backflow preventer device that is simple in its design and operation, not visible from publicly accessible areas, tamper-resistant, easy to install in any plumbing piping configuration, essentially maintenance free, and truly cost-effective to manufacture, install and operate.